Mixers and pumps have a wide range of applications including bioreactors. The main elements in a mixer 100 (FIG. 1A) are the drive 14 (which contains the driving mechanism) and the impeller 12 (which contains the mixing blades), at the impeller end 11. The two elements are coupled together by different topologies. In one aspect, the magnetic coupling is where the impeller 12 holds a set of magnets 10 that are coupled to the drive end 13. This is established by a set of magnets in the drive end rotated by a separate motor. The existing technology contains a set of cylindrical magnets 14 (See FIG. 1B) on each end separated by a certain “magnetic” gap 16 which is primarily composed of air, fixing elements, and mixing bag wall which are all non-magnetic elements. The existing technology suffers many impediments, including, but not limited to: (1) the weak coupling between the magnets which requires using more expensive and larger magnets (e.g., Neodymium magnets), (2) poor volume utilization, (3) the use of rare-earth magnets in the impeller which is a single use element that increases the cost of the impeller and poses environmental challenges, and (4) large drive size, as it constructs of a set of large coupling magnets driven by a separate electrical motor.
Mixing systems often include an agitator or impeller mechanically connected to a drive shaft lowered into a fluid through an opening in the top of a vessel. The drive shaft is connected to an electric motor arranged outside the vessel. In a closed vessel, a fluid seal is provided between the drive shaft and the wall of the vessel to prevent leakage of fluid from the vessel. Other mixing systems include a rotating magnetic drive head outside of the vessel and a rotating magnetic impeller as an agitation element within the vessel. The movement of the magnetic drive head enables torque transfer and thus rotation of the magnetic impeller allowing the impeller to mix and agitate the fluid within the vessel. Because there is no need in a closed vessel to have a drive shaft penetrate the vessel wall to mechanically rotate the impeller, magnetically coupled systems can eliminate the need for having fluid seals between the drive shaft and the vessel. Magnetic coupling of an impeller inside the vessel to a drive system or motor external to the vessel can eliminate contamination issues, allow for a completely enclosed system, and prevent leakage.
Increasingly, in the biopharmaceutical industry, single use or disposable containers or vessels are used as close type systems, typically in range of about 1-2000 liters. The vessel may be a tank-type support with for example substantially cylindrical shape and is made of rigid material such as stainless steel to provide sufficient support for the flexible bag or container, for example of a kind used in single-use bioreactors. Use of sterilized disposable bags eliminates time consuming steps of cleaning of the vessel and reduces the chance of contamination. The flexible container or bag is placed inside the vessel in an accurate manner so that for example different pipelines or tubes, mixers and sensors can be connected to the bag properly and accurately.
Combining the single use or disposable bags with a magnetic agitator system establishes a sterile environment that is utilized in biopharmaceutical manufacturing. A variety of vessels, devices, components and unit operations for mixing and manipulating liquids and/or for carrying out biochemical and/or biological processes are available. For example, biological materials including mammalian, plant or insect cells and microbial cultures can be processed using bioreactors that include single-use processing bags. Manufacturing of complex biological products such as proteins, monoclonal antibodies, etc. requires, in many instances, multiple processing steps ranging from fermentation or cell culture (bacteria, yeast, insect, fungi, etc.), to primary recovery and purification.
It is desirable to address the needs as stated above by utilizing less expensive elements that are more environmentally friendly. Aspects of the invention will run a much smaller impeller, and have a reduced magnetic force that will allow the bag to be separated from the drive more easily. Further, moving parts on the drive (user) end will be addressed to provide safer mechanisms.